The invention relates to an apparatus for contacting a liquid with a gas. More particularly, the present invention relates to an apparatus comprising a normally vertically extending column having a plurality of substantially horizontal trays arranged in the column one above the other, each of the trays being provided with apertures or openings for the passage of gas and with at least one means for downward transfer of liquid, the means for downward transfer of liquid providing liquid flow from the upper side of a given tray to a point below the tray, and the means for downward transfer of liquid comprising means for discharge of liquid. As used herein, the term "gas" is to be understood to include vapor.
Apparatuses of the above-mentioned type are employed in processes such as distillation, absorption and stripping. Examples of trays which may be utilized in such apparatuses are grid trays, which are formed of parallel bars that may be straight or curved and are spaced apart to leave slots between them; sieve plate trays, which are formed of plates that are punched or otherwise fabricated to have circular or other openings in them; and valve trays, which are sieve trays provided with valves being displaceably arranged in the openings of the trays.
The trays may be provided with a plurality of means for downward transfer of liquid, the means having any suitable shape. The longitudinal cross-section of such means is preferably oblong, since such a shape renders it possible to arrange the means in an optimal manner on a tray and insure during operation a uniform distribution of liquid over the tray and a uniform supply of liquid to the next lower tray. In the case where such apparatuses are intended for high liquid loads, the means for downward transfer of liquid occupy a considerable part of the tray area. The liquid discharge means or openings in the means for downward transfer of liquid may be arranged in the bottoms or side of the means or devices. When the trays are provided with a plurality of relatively closely packed devices for downward transfer of liquid, required for high liquid loads, it is advantageous to arrange the liquid discharge openings in the bottoms of the devices or to provide the devices with open lower ends. In this manner, interference of liquid streams from liquid discharge openings of adjacent devices is prevented.
When the liquid discharge openings are arranged in the bottoms of the devices, another problem may occur, especially when operating at high liquid loads. The liquid leaving the openings in the bottoms of the means or devices for downward transfer of liquid normally falls with such a velocity on to the next lower tray that the liquid may pass directly through the tray openings below the devices, in the case of sieve plate trays, or, if valve trays are used, may push the valves directly below the devices downwards, thereby closing the openings in the next lower tray. The consequence of such liquid flow is that the active tray area, i.e., the tray area not occupied by means or devices for downward transfer of liquid, is not fully used for the passage of gas. The gas is not, therefore, uniformly distributed over the whole active tray area, and, as a consequence thereof, the space above a tray is not optimally employed for contact between gas and liquid. It is an object of the invention to provide a tray apparatus for contacting a liquid with a gas, the apparatus having active tray areas which can be optimally used for gas/liquid contact, even when the apparatus is operated at high liquid loads.